Switch control circuit for automatic telephone systems



March 240 1925.

A. B. SMITH SWITCH CONTROL CIRCUIT FOR AUTOMATIC TELEPHONE SYSTEMS Filed Sept. 19, 1919 ll 1 w n F\G.S

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UNITED STATES PATENT OFFICE.

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Application filed September 19, 1919. Serial Ito. 824,997.

To all whom it may concern? Be it known that I, ARTHUR BESSEY SMITH, acitizen of the United States of America, and a resident of Evanston, in the 5 county of Cook and State of Illinois, have invented certain new and useful Improve:

ments in Switch Control Circuits for Automatic Telephone Systems, of which the fol lowing is a specification.

My invention relates in general to circuits for automatic switches, but more particularly to such circuits as extend over. long aerial hnes, or which include a sectionv of cable, and which therefore have considerable electrostatic capacity; and the object of the invention is to provide an improved cir- Y cuit arrangement wherein the effect of line capacity is neutralized, thereby permitting automatic switches to be controlled accurately and certainly. v

I have shown in Fig. 1 of the drawing that embodiment of the invention which I consider to be the best; and in Figs. 2 to 7,

inclusive, I have shown certain modificw, tions of the invention which produce the desired results more or less perfectly in somewhat different, ways. The modifications shown in Figs. 6 and 7 are not claimed heree in, but are claimed in my divisional app1ication Serial No. 603,934, filed November 29, 1922.

Referring to Fig, 1, the reference character L indicates a line of high electrostatic capacity, and which may be a so called simplex circuit superimposed on a toll or long distance line. B isja relay adapted to be energized by the closure of the switch S- and which may thereafter be intermittently deenergized by operation of the calling device D to produce a series of interruptions in the circuit of the line L. This circuit in:

" eludes at the opposite end of the line the relay R: which responds, upon the initial closure of the line circuit to complete a switch control circuit over conductors L and L and which deenergizes thereafter responsive to interruptions in the,line circuit to reproduce such interruptions in the switch control circuit.

above are well known in the art. Relay R may be a relay of a repeater located in a particular exchange, which repeater is accessible to calling subscribers for enabling control j1s short-circuited and therefore Circuits corresponding to thosedescribed them to establish connections over the toll line with which the repeater is associated; while relay R may be a relay of another repeater at the opposite end of the toll line,

automatic switches to complete such connections to the desired called lines, all of which is well understood, aspreviously stated.

I will now proceed to explain the operation of my invention. Referring to Fig. 1, and neglecting for a moment the condenser G and battery B or rather, assuming that whose function it is to control one or more they are not present, it will be seen that when relay R is energized, the negative pole of 'grounded'battery B is connected to line L, thereby causing a currentflow overthesaid line and resulting in the energize.- tion of relay R to become charged negatively by reason of its electrostaticcapacity with regard to the is momentarily circuit, current' at the distant end. At the a i same t1me,-the line conductor may. be said it does not do-this, but re- I for an instant after its cir- 1 mitted over the circuit. T is faulty operation is due to the charge on the line, which at each interruption of the circuit flows off.

through the relay R to ground and thus holds the said relay energized for an instant after each interruption, or more generally speaking, renders it sluggish in responding to interruptions of the circuit.

Consider now the effect of condenser C and battery B connected as shown in Fig.

1. While relay R is energized the condenser g i completely discharged. Now when the rela R (lo-- energizes and interrupts the line clrcuit, the condenser is connected from theline to thepositive pole of grounded battery B, from which it will appear that the negative charge on the line willifiow into the condenser, in a manner of speaking, and charge it, this opposite side of the condenser-is connected to the positive pole ofthe grounded battery,

action being assisted 'bythe fact that the instead of direct to ground. It will thus be seen that the condenser affords a means for dissipating the line charge, whereby a large portion of it is prevented from flowing thru the relay R to ground. Relay R becomes much more quicklyv responsive to interruptions in its circuit and the process of transmitting switch controlling impulses is rendered certain and dependable. 7

Taking up the modifications now, these will be easily understood without extended explanation. Fig. 2 shows means for directly grounding the line circuit between interruption, which is found to be helpful in certain cases. The arrangement shown in Fig. 3 resembles that shown in Fig. 1 in that a condenser is used which is short-circuited while the line circuit is closed and which is connected from the line to ground during interruptions. No battery is used however, in connection with the condenser. In Fig. 4 a. battery of reversed polarity operates directly without the interposition of a condenser to take care of the line charge. With this arrangement a rather high resistance must be used to prevent the reverse current flow from rising to too high a value before the end of the interruption of the line circuit. An improvement on this idea, Fig. 5, uses a relay of low resistance which on operating inserts a high resistance in series with its own winding to limit the current flow. Fig. 6 may be considered an improvement on Fig. 3. A condenser is connected from the line to ground during interruptions of the line'circuit, as in Fig. 3; but when the line circuit is closed the condenser is oppositely charged insteadof merely being short-circuited. The condensertherefore, need only be half as large. The last modification, Fig. 7 uses a condenser oppositely charged but dispenses with the extra battery, the circuit arrangement be ing such that during closures of the line' circuit the condenser is oppositely charged by the main battery.

Other modifications than those pointed out above will doubtless occur to persons skilled in the art; and the inventionwill' no doubt be found to be of utility under circumstances difiering from those specifically mentioned. I do not, therefore, wish to be held to the exact form of the invention disclosed herein, but desire to include and have protected by Letters Patent all variations thereof which come within the scope of the appended claims.

What I claim as my inventionis:

1. In a telephone system, a ground return line circuit having a relay at one endv responsive todirect current, said line having high electrostatic capacity, two batteries at the other end, one battery having the positive pole grounded and the other the negative, both batteries beingdirectly connected line.

2. In a telephone system, a ground return lme circuit having a relay at one end responsive to direct current, said linehaving high electrostatic capacity, two batteries at the other end, one battery having the positive pole grounded and the otherthe negative, means for-closing the line circuit thru one battery to operate said relay, means for intermittently interrupting the circuit to produce deenergizations of said relay, means for closing the line circuit thru the said other battery each time the circuit is interrupted to discharge the line, and a resistance in series with said second battery to prevent said relay from energizing.

3. In a telephone system, a ground return line circuit having a relay at one end, said line having high electrostatic capacity, two,

batteries at the other end, one battery having the positive pole rounded and the other the negative, means or closing the line circuit thru one battery to operate said relay, means for intermittently interrupting the circuit to produce deenergizations of said relay, a condenser, means for connecting the line by way of said condenser to the said other battery to discharge the line each timev the circuit is interrupted, and means for discharging said condenser each time the circuit is closed.

4. In a telephone system, a line circuit including a relay, a condenser, said line circuit normally connected through said condenser to a battery of one polarity at the end opposite the relay, and means for switching said end of the line circuit into connection with a battery of the opposite polarity to energize said relay and for short circuiting said condenser to dissipate the charge collected from the line.

5. In a telephone system, a line circuit in cluding a first relay, a condenser, a second relay for controlling said line circuit in response to impulses, said second relay maintaining said line circuitconnectcd through said condenser to a battery of one polarity normally to discharge the line circuit, and energized to short circuit said condenser and to connect the line circuit to a battery. of another polarity to energize said first relay.

6. In a telephone system, a line circuit including a relay, a condenser, means for sending impulses of current over said line circuit.

from a battery of one polarity and for connecting said line circuit through said condenser to a battery of the op osite polarity to remove the charge from t e line circuit between impulses, and additional means for discharging said condenser during iinpulses.

T. In a telephone system, a line circuit including a relay, batteries of opposite polarity, a condenser, means for sending impulses of any desired duration from one of said batteries over said line circuit to operate said relay, and for connecting said line circuit through said condenser to the other battery between impulses to assist in the deenergization of said relay.

8. In a telephone system, a ground return line circuit having a non-polarized relay at one end normally responsive to continuous current in either direction, two batteries at the other end, one battery having the positive pole grounded and the other the negative, means for connecting said batteries in the line circuit alternately, one-battery being ell'ective to cause encrgizations of saidrelay and the other battery being eflective to reverse the current in the line to cause the relay to deenergize quickly, and means for preventing said relay from again energizing while the current is reversed.

t). In a telephone system, a ground return line circuit having a non-polarized relay at one end normallyresponsive to continuous current in either direction, two batteries at the other end, one battery having the positive pole grounded and the other the negative, means for closing the line circuit through one battery to operate said relay,

means Ltor interrupting the circuit to produce deenergizations of said relay, means for closing the line circuit through the second battery each time the circuit is interrupted to reverse the current in the line and thereby cause said relay to deenergize more quickly, and a resistance in series with said second battery to prevent the said relayfrom energizing while the current is reversed.

10. In combination, a ground return line circuit including a relay at one end, a bat tery, a condenser, and a second relay at the other end of the line, means for energizing and deenergizing said second relay, and contact springs controlled by said second relay for closing the line circuit through said battery and for short-circuiting said condenser when the relay is energized, and for connecting the line to ground through said condenser when the relay is deenergized.

11.. In combination, a line circuit terminating in a relay at one end, a battery atthe other end, a second relay and means for energizing it to connect said battery in the line circuit to energize said first relay, means for intermittently deenergizing said second relay to produce interruptions in the current flow, a condenser, means for temporarily connecting said condenser in shunt of said first relay to discharge the line each time said second relay deenergizes, and means for short-circuiting said condenser to discharge it each time said second relay energizes.

12. In combination, a ground return line circuit having a relay included at one end and a battery at the other, means for intermittently interrupting the line circuit to 0perate said relay, a condenser, a shunt path from the line to ground through said condenser, means for opening said shunt when the line circuit is closed and for closing it to discharge the line each time the line circuit is interrupted, and means comprising a shunt circuit excluding any current source for discharging the condenser each time the line circuit is closed.

13. In combination, a line circuit including a battery at one end and a relayat the other end, a condenser, a charge collecting circuit including said line and condenser but excluding said battery, a discharge circuit for said condenser excluding said relay and said battery, and a relay having contact springs for closing the line and discharge circuits when energized and the charge collecting circuit when deenergized.

14. In combination, a line circuit including a battery at one end and a relay at the other end, a condenser, a charge collecting circuit including said line and condenser but excluding said battery, a discharge circuit for said condenser excluding said-relay and said battery, and a two position electromagnetic switch having contacts for clos ing said line and discharge circuits inone position and said charge collecting circuit in the other position.

Signed at Chicago, Cook County, this 13th day of September, 1919.

ARTHUR BESSEY SMITH.

Illinois, 

